This invention relates to devices having coatings deposited thereon and their method of production. Specifically, this invention relates to devices, and their method of production, having coatings deposited by pulsed plasma polymerization of a macrocycle containing a heteroatom, wherein the heteroatom is oxygen, nitrogen, sulfur, or a mixture thereof. More specifically, this invention relates to devices, and their method of production, having coatings deposited by gas phase polymerization of a cyclic ether, which coatings are non-fouling and wettable, and the gas phase polymerization utilizes a pulsed discharge.
Non-biologically fouling, wettable thin film surface coatings are of interest for use in improving the biocompatibility of contact lenses. Coatings containing ethylene oxide (--CH.sub.2 --CH.sub.2 --O).sub.n ("EO") units are quite effective in providing non-fouling, relatively hydrophilic surfaces. In particular, it has been recently demonstrated that under continuous-wave conditions, volatile, low molecular weight molecules containing relatively few EO units can be plasma polymerized onto surfaces to provide wettable, non-fouling thin film coatings [G. P. Lopez, B. D. Ratner, C. D. Tidwell, C. L. Haycox, R. J. Rapoza, and T. A. Horbett, "Glow discharge plasma deposition of tetraethylene glycol dimethyl ether for fouling-resistant biomaterial surfaces," J. Biomed. Mater. Res., 26,415-439 (1992). D. Beyer, W. Knoll, H. Ringsdorf, J.-H. Wang, R. B. Timmons, and P. Sluka, "Reduced protein adsorption on plastics via direct plasma deposition of triethylene glycol monoallyl ether," J. Biomed. Mater. Res., 36, 181-189 (1997)]. U.S. patent application Ser. No. 09/115,860 disclosed that monomers containing as few as two EO units per molecule, when plasma polymerized under low power input conditions made available by the variable duty cycle pulsed plasma technique, yielded strongly adherent, wettable, and non-fouling coatings when deposited on the surfaces of contact lenses. The monomers employed involved only non-cyclic linear or branched olefinic compounds.
Cyclic ethers, more commonly referred to as crown ethers, represent a separate class of EO molecules containing several oxygen atoms, usually in a regular pattern. Recent reports have shown that continuous-wave plasma polymerization of these compounds can provide surface coatings which exhibit a modest level of biomolecule rejection [E. E. Johnston, B. D. Ratner, and J. D. Bryers, "RF plasma deposited PEO-like surfaces that inhibit Pseudomonas aeruginosa accumulation," Polym. Mater. Sci. and Engi. (Abstracts), 77, p. 577 (1997). E. E. Johnston and B.D. Ratner, "The effects of linear and cyclic precursors on the molecular structure of ether-rich plasma-deposited films," Mater. Res. Soc. (Abstracts), p. 464, December 1998 (Boston, Mass.); E. E. Johnston, B. D. Ratner and J. D. Bryers, NATO ASI Series E, Applied Science, Vol 346, pp.465-476, (1997)]. In this work, reduced fouling was demonstrated with measurements of Pseudomonas aeruginosa adherence to plasma modified surfaces versus uncoated glass surfaces. For example, an approximate 40% reduction in Ps. Aeruginosa adherence was observed on plasma polymerized 12-crown-4 (C.sub.8 H.sub.16 O.sub.4) surfaces relative to that observed with uncoated glass, as estimated from the graphic data provided [E. E. Johnston, B. D. Ratner, and J. D. Bryers, "RF plasma deposited PEO-like surfaces that inhibit Pseudomonas aeruginosa accumulation,"Polym. Mater. Sci. and Engi. (Abstracts), 77, p. 577 (1997)]. Slightly higher reduction in adsorbed bacteria (i.e., a few percent higher) was reported on coatings obtained from the plasma polymerization of 15-crown-5 (C.sub.10 H.sub.20 O.sub.5). The level of protein adsorption was observed to be independent of the power input provided during the plasma polymerization of this monomer. Additionally, the crown ether compounds were shown to be considerably less efficacious than coatings obtained from linear, saturated EO containing molecules (commonly referred to as glymes) of general formula CH.sub.3 (OCH.sub.2 CH.sub.2).sub.n OCH.sub.3. For example, tetraglyme (C.sub.10 H.sub.22 O.sub.5) was shown to reduce Ps. Aeruginosa surface adsorption by a factor of at least five times more than that observed with the comparable molecule weight 15-crown-5 monomer. Furthermore, the tetraglyme coatings deposited at higher plasma power (20 W) were shown to adsorb less bacteria than that obtained on coatings deposited at 5 W [E. E. Johnston, B. D. Ratner, and J. D. Bryers, "RF plasma deposited PEO-like surfaces that inhibit Pseudomonas aeruginosa accumulation," Polym. Mater. Sci. and Engi. (Abstracts), 77, p. 577 (1997)]. Thus, in summary, the reported work showed that: (1) The accumulation of bacteria onto the linear glyme films was much lower than that on the crown ether films, indicating that cyclic ethers produce significantly poorer non-fouling coatings than the linear glyme molecules when deposited as plasma polymer films on substrates; and (2) the efficacy of the plasma films in functioning as non-fouling coatings is either independent of the power employed during the plasma deposition (as shown for cyclic ethers) or they become less efficacious with decreasing power (as shown for the linear glyme).
Additional notable aspects of the prior studies is that samples to be coated were located upstream of the plasma discharge zone, apparently in order to improve retention of the EO content in the plasma films [E. E. Johnston, B. D. Ratner, and J. D. Bryers, "RF plasma deposited PEO-like surfaces that inhibit Pseudomonas aeruginosa accumulation," Polym. Mater. Sci. and Engi. (Abstracts), 77, p. 577 (1997); E. E. Johnston, B. D. Ratner and J. D. Bryers, NATO ASI Series E, Applied Science, Vol 346, pp. 465-476, (1997)]. Also, a relatively high (80 W) initial deposition was employed to provide a sub-surface which was apparently required to enhance adhesion of the subsequent outermost layers deposited at lower power inputs [E. E. Johnston, B. D. Ratner, and J. D. Bryers, "RF plasma deposited PEO-like surfaces that inhibit Pseudomonas aeruginosa accumulation," Polym. Mater. Sci. and Engi. (Abstracts), 77, p. 577 (1997); E. E. Johnston, B. D. Ratner and J. D. Bryers, NATO ASI Series E, Applied Science, Vol 346, pp. 465-476, (1997)].